This invention relates to a photopolymerizable composition, more particularly to a photopolymerizable composition containing a special photo initiator.
Photopolymerizable compositions are widely used for preparing letterpresses, relief images, photoresists, and the like by using a UV light source in general, and are desired to have higher sensitivity. Particularly when scanning exposure to light by using a laser beam is aimed at, it is necessary to have high sensitivity to visible light, for example, major output wavelengths of 458, 488, and 514 nm in the case of an argon ion laser. Heretofore, there have been made various studies on photo initiators in this field for increasing the sensitivity. As to the photo initiators, there have been known a number of substances such as benzoin and derivatives thereof, substituted or non-substituted polynuclear quinones, etc., but there have not been known those having sufficient sensitivity particularly to the visible light.
On the other hand, there are known compositions comprising an N-aryl-.alpha.-amino acid such as N-phenylglycine and various photo-absorbing compounds (e.g. Japanese Patent Unexamined Publication No. 57-83501). But these compositions are insufficient in sensitivity and have various disadvantages in that there is a problem of a bad odor, adhesiveness to a copper-clad laminate is insufficient, storage stability is poor, and the like.